1. Field of the Invention
The present invention relates to an ink-jet printer, and more particularly to a heat generating type ink-jet print head including an ink supply passage for receiving ink from an ink container, a micro chamber for storing the ink and nozzles, all being directly formed on a substrate, and a method for fabricating the ink-jet print head using the electrolytic polishing process.
2. Description of the Prior Art
The expanded use of computers has resulted in an abrupt increase in the requirement of inexpensive printers having a superior performance. Heat generating type ink-jet printers have been known as satisfying the above requirement on the basis of the following reason. Such heat generating type ink-jet printers have the advantages of easy application to a digital computer, high resolution, high speed, color printing function and low cost, as compared to dot matrix printers and laser printers.
An ink-jet printer is most suitable for a portable computer because of its low requirement of energy per dot as compared to other printer systems and no requirement of any small and heavy mechanical elements. An ink-jet printer also has the advantages of the elimination of noise by virtue of its non-impact system, reduced cost by virtue of consumption of ink only as dots require, easy maintenance and high applicability to technical fields by virtue of its non-contact system.
Of various elements constituting such heat generating type ink-jet printers, the highest value-added and technology-intensive ones are ones with the head adapted to inject the ink.
If there is no independent fabrication and design capability for ink-jet print heads, then it is impossible to independently design other elements (additionally, mechatronics and software) constituting a printer. In the case of ink-jet printers, therefore, the independent fabrication and design capability for ink-jet print heads is very important.
Hewlett Packard Company in the U.S.A. and Canon Company in Japan are the leading companies in producing heat generating type ink-jet print heads. Although products made by these companies are operated in the same principle manner, they have a difference in the ink injection direction. That is, the product made by Hewlett Packard Company has an upward ink injection direction, while the product made by Canon Company has a lateral ink injection direction. Although the products of both companies have individual advantages and disadvantages, the present invention embodies a heat generating type ink-jet print head having the upward ink injection direction, as in the product of Hewlett Packard Company, using an electrolytic polishing process.
Now, a heat generating type ink-jet print head produced by Hewlett Packard Company will be described in conjunction with FIG. 1.
As shown in FIG. 1, the head is attached at its lower surface to the upper surface of a ink container 1. The head includes the main ink supply passage 2, vertically extending throughout a substrate 14 of the head and serving to supply ink .from the ink container 1 towards the upper surface of the head. The head also includes an assistant ink supply passage 3 communicating with the main ink supply passage 2. The assistant ink supply passage 3 serves to supply the ink from the main ink supply passage 2 to a micro-chamber 4. The head also includes a nozzle 5 for injecting the ink contained in the micro-chamber 4 onto a sheet 13.
The ink injection is achieved as a heat generating resistor film 6, formed on the micro-chamber 4, generates a thermal energy which, in turn, abruptly expands the volume of the ink. To this end, the head has a wiring for applying the electrical energy to the heat generating resistor film 6 and a pad 8 for coupling the wire 7 to an external energy source.
The head also includes a non-conductor protection film 9 and a metal protection film 10 in order to protect the heat generating resistor film 6 and the wire 7 from mechanical impact generated upon the ink injection and an erosion caused by the ink. A thermal insulating film 11 is formed beneath the heat generating resistor film 6 so as to efficiently use the heat generated at the heat generating resistor film 6 as the ink injection energy. The micro-chamber 4 is defined by a thermal insulator 12.
This conventional head, having the above-mentioned structure, is fabricated using the method including the steps of forming constituting elements of the head up to the micro-chamber on the substrate, forming the main ink supply passage using a laser or sand striking process, and then covering a nozzle plate, provided with the nozzle, over the resulting structure obtained after the formation of the main ink supply passage.
However, this fabrication method has the following problems.
First, it involves high manufacturing costs because it uses expensive laser equipment and specific equipment for arranging the nozzle plate and the substrate.
Second, it involves low productivity because the formation of the main ink supply passage and the covering of the nozzle plate are not carried out by the unit of wafer, but carried out by the unit of head.
Third, it involves severe generation of dust and crack and the difficulty in fabricating a high resolution and wide-width ink-jet print head having a smaller-size main ink supply passage because the main ink supply passage is mechanically formed.